Create keeko:publish command

[gossi]

A keeko publish command needs to do the following tasks:

• Ask for the version number (or suggests one?) if none is provided
• Generate the required git tag
• Needs to collect all migrations and makes them executable from the Module::update() class
• Manages composer packages in composer.json so it can be installed via composer over packagist

Bonus:

• Collects all closed issues since the release before and creates a changelog
• Uses the github API to create a release and put the changelog inside